Recently, the VOD delivery streaming specifications have been standardized, and client terminals in conformance with the standard, such as Internet televisions and Set Top Boxes (STBs), have been reduced to practice. Hence, the VOD delivery is made as a part of a large-scale IPTV (Internet Protocol TeleVision).
Te VOD delivery streaming specifications that have been standardized include the following with respect to encoding of moving pictures or dynamic images and audio information related thereto.
“ISO/IEC 13818 Generic coding of moving pictures and associated audio information”
Recently, the stream delivery of the VOD or broadcasting service in conformance with the MPEG2 Transport Stream (MPEG2-TS), which can deliver a plurality of programs in one stream (or data sequence), is becoming more popular due to the increase in the number of users of the Internet, the more popular use of optical lines, and the increase in the communication speeds of communication networks.
The delivery in accordance with the MPEG2-TS sends the stream based on a Program Clock Reference (PCR), that is, time reference information to be referred to when performing a synchronized reproduction. On the other hand, at a client, the video and/or audio encoded data sequence is decoded and output as a reproduced output based on time management information (PTS: Presentation Time Stamp) of the reproduced output and time management information (DTS: Decoding Time Stamp) for decoding the data sequence.
The VOD delivery includes a pay-delivery which is a video content purchasing and accounting type, and a free-delivery which is an advertising type. In the case of a free-delivery model of the advertising type, the stream delivery of the advertising content may be made according to a client-led delivery system or a server-led delivery system. The client-led delivery system acquires a desired play list to be viewed when making a first connection at the client end, and successively requests delivery of a main part of the video content and the advertising content according to the play list at the client end, in order to make the delivery according to the requests.
FIG. 1 illustrates an example of an operation of the client-led delivery system. According to this delivery system, a client 20 first requests a play list with respect to a VOD server 10, and acquires from the VOD server 10 a play list 21 of an advertisement A and a main part (sequence 6-1). In the following description, a “client terminal” will be referred to as a “client”, a “main part of the video content” will be referred to as a “main part”, and an “advertising content” will be referred to as an “advertisement”.
The client 20 requests viewing of the advertisement A to the VOD server 10 according to the play list 21, and the VOD server 10 delivers a stream of the advertisement A to the client 20 according to the viewing request (sequence 6-2). After the delivery of the advertisement A ends, the client 20 requests viewing of the main part, and the VOD server delivers a stream of the main part to the client 20 according to the viewing request (sequence 6-3).
FIG. 2 schematically illustrates an example of the client-led delivery system. If it is assumed for the sake of convenience that the play list 21 of the advertisement A and the main part has been acquired at the client 20, the client 20 sends to the VOD server 10 the request to view the advertisement A according to the play list 21. At the VOD server 10, when a receiving part 11 receives the request to view the advertisement A, the VOD server 10 sends the stream of the advertisement A to a delivering part 12, and the delivering part 12 delivers the stream of the advertisement A to the client 20.
At the client 20, after delivering the advertisement A, the request to view the main part is sent to the VOD server 10. When the receiving part 11 of the VOD server 10 receives the request to view the main part, the VOD server 10 sends the stream of the main part to the delivering part 12 according to the request to view the main part, and the delivering part 12 delivers the stream of the main part to the client 20.
In the client-led delivery system, the advertising content is delivered at a header portion or a trailer portion of the main part content in most cases. On the other hand, in the server-led delivery system, the server initially creates a stream in which the advertisements are inserted at intermediate portions of the main part, and delivers the stream of the main part created in advance and inserted with the advertisements in respect to a delivery request.
FIG. 3 schematically illustrates the state of delivery of the server-led delivery system. First, a preparation is made in advance at the VOD server 10 to create in advance the stream in which the advertisements are inserted at intermediate portions of the main part. For example, a first main part stream (to be delivered) is created in advance by inserting advertisements A and B into the main part and subjecting the main part to encoding and multiplexing. This first main part stream is stored in a storage unit such as a hard disk drive.
For example, as illustrated in FIG. 3, a main part stream (a) added with time information 1 through 10 is inserted with a stream (b) of the advertisement A added with the time information 1 through 3 and a stream (c) of the advertisement B added with the time information 1 through 3, and subjected to encoding and multiplexing to thereby create in advance, as one content, a first main part stream (d) (to be delivered).
FIG. 3 illustrates a case where the advertisement A is inserted into the main part before the time information 5, and the advertisement B is inserted into the main part before the time information 9. In this case, the time information 1 through 3 of the advertisement A is changed to time information 5 through 7 in the first main part stream (d) (to be delivered), and the time information 5 through 8 of the main part is changed to time information 8 through 11 in the first main part stream (d) (to be delivered).
In addition, the time information 1 through 3 of the advertisement B is changed to time information 12 through 14 in the first main part stream (d) (to be delivered), and the time information 9 and 10 of the main part is changed to time information 15 and 16 in the first main part stream (d) (to be delivered).
Hence, when the client 20 sends a request to view the first main part (to be delivered) as illustrated in FIG. 4, the VOD server 10 delivers to the client 20 the first main part stream (d) (to be delivered), which is created and stored in advanced and is inserted with the advertisements A and B.
According to the conventional server-led delivery system, when switching the advertisements, it is necessary to again make the preparation in advance. For example when the advertisements A and B are to be switched to advertisements C and D, a second main part stream (h) (to be delivered) and illustrated in FIG. 3 is created.
In other words, a main part stream (e) added with time information 1 through 10 is inserted with a stream (f) of the advertisement C added with the time information 1 through 3 and a stream (g) of the advertisement D added with the time information 1 through 3, and subjected to encoding and multiplexing to thereby create in advance, as one content, the second main part stream (h) (to be delivered).
In this case, even if a main part stream (e) is identical to the main part stream (a), the second main part stream (h) (to be delivered) must be created as a separate content, similarly to the first main part stream (d) (to be delivered).
For example, a Japanese Laid-Open Patent Publication No. 2005-160032 proposes a system that delivers digital contents such as video and music from a VOD server and reproduces the digital contents in a terminal equipment of the viewer.
When delivering the advertisements, the conventional client-led delivery system acquires the play list at the client when making the first connection. The request to view the main part and the request to view the advertisement must be made separately according to the play list, and there is a problem in that a seamless switching cannot be made between the main part and the advertisement.
In addition, in the conventional server-led delivery system, the VOD server must create in advance the stream in which the advertisements are inserted into the main part, subjected to encoding and multiplexing, and stored in the storage unit such as the hard disk drive. For this reason, even if the same main part is to be delivered, a plurality of kinds of main part streams inserted with different advertisements must be created and stored in the storage unit such as the hard disk drive if the different advertisements are to be delivered to different clients. As a result, the storage capacity of the storage unit such as the hard disk drive is easily used up by the main part streams to be stored therein.